/*
  Copyright (c) 2014 Dimitrij Gester

  "Smart RC TX" is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  "Smart RC TX" is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General
  Public License along with "Smart RC TX"; if not, write to the
  Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  Boston, MA  02111-1307  USA
*/


#ifndef CRC_H_
#define CRC_H_

#define CRC8_TABLE
#undef CRC8_TABLE


#ifdef WIN32

#include "typ.h"


// The 1-Wire CRC scheme is described in Maxim Application Note 27:
// "Understanding and Using Cyclic Redundancy Checks with Maxim iButton Products"
#ifdef CRC8_TABLE
// This table comes from Dallas sample code where it is freely reusable,
// though Copyright (C) 2000 Dallas Semiconductor Corporation
static const uint8_t dscrc_table[] = {
	0, 94,188,226, 97, 63,221,131,194,156,126, 32,163,253, 31, 65,
	157,195, 33,127,252,162, 64, 30, 95,  1,227,189, 62, 96,130,220,
	35,125,159,193, 66, 28,254,160,225,191, 93,  3,128,222, 60, 98,
	190,224,  2, 92,223,129, 99, 61,124, 34,192,158, 29, 67,161,255,
	70, 24,250,164, 39,121,155,197,132,218, 56,102,229,187, 89,  7,
	219,133,103, 57,186,228,  6, 88, 25, 71,165,251,120, 38,196,154,
	101, 59,217,135,  4, 90,184,230,167,249, 27, 69,198,152,122, 36,
	248,166, 68, 26,153,199, 37,123, 58,100,134,216, 91,  5,231,185,
	140,210, 48,110,237,179, 81, 15, 78, 16,242,172, 47,113,147,205,
	17, 79,173,243,112, 46,204,146,211,141,111, 49,178,236, 14, 80,
	175,241, 19, 77,206,144,114, 44,109, 51,209,143, 12, 82,176,238,
	50,108,142,208, 83, 13,239,177,240,174, 76, 18,145,207, 45,115,
	202,148,118, 40,171,245, 23, 73,  8, 86,180,234,105, 55,213,139,
	87,  9,235,181, 54,104,138,212,149,203, 41,119,244,170, 72, 22,
	233,183, 85, 11,136,214, 52,106, 43,117,151,201, 74, 20,246,168,
116, 42,200,150, 21, 75,169,247,182,232, 10, 84,215,137,107, 53};

//
// Compute a Dallas Semiconductor 8 bit CRC. These show up in the ROM
// and the registers.  (note: this might better be done without to
// table, it would probably be smaller and certainly fast enough
// compared to all those delayMicrosecond() calls.  But I got
// confused, so I use this table from the examples.)
//
uint8_t crc8_update(uint8_t crc, uint8_t data)
{
	return *(dscrc_table + (crc ^ data));
}
#else
//
// Compute a Dallas Semiconductor 8 bit CRC directly.
// this is much slower, but much smaller, than the lookup table.
//
uint8_t crc8_update(uint8_t crc, uint8_t data)
{
	uint8_t inbyte = data;
	for (uint8_t i = 8; i; i--) {
		uint8_t mix = (crc ^ inbyte) & 0x01;
		crc >>= 1;
		if (mix) crc ^= 0x8C;
		inbyte >>= 1;
	}
	return crc;
}
#endif

#else

#include <avr/pgmspace.h>

// The 1-Wire CRC scheme is described in Maxim Application Note 27:
// "Understanding and Using Cyclic Redundancy Checks with Maxim iButton Products"
#ifdef CRC8_TABLE
// This table comes from Dallas sample code where it is freely reusable,
// though Copyright (C) 2000 Dallas Semiconductor Corporation
static const uint8_t PROGMEM dscrc_table[] = {
      0, 94,188,226, 97, 63,221,131,194,156,126, 32,163,253, 31, 65,
    157,195, 33,127,252,162, 64, 30, 95,  1,227,189, 62, 96,130,220,
     35,125,159,193, 66, 28,254,160,225,191, 93,  3,128,222, 60, 98,
    190,224,  2, 92,223,129, 99, 61,124, 34,192,158, 29, 67,161,255,
     70, 24,250,164, 39,121,155,197,132,218, 56,102,229,187, 89,  7,
    219,133,103, 57,186,228,  6, 88, 25, 71,165,251,120, 38,196,154,
    101, 59,217,135,  4, 90,184,230,167,249, 27, 69,198,152,122, 36,
    248,166, 68, 26,153,199, 37,123, 58,100,134,216, 91,  5,231,185,
    140,210, 48,110,237,179, 81, 15, 78, 16,242,172, 47,113,147,205,
     17, 79,173,243,112, 46,204,146,211,141,111, 49,178,236, 14, 80,
    175,241, 19, 77,206,144,114, 44,109, 51,209,143, 12, 82,176,238,
     50,108,142,208, 83, 13,239,177,240,174, 76, 18,145,207, 45,115,
    202,148,118, 40,171,245, 23, 73,  8, 86,180,234,105, 55,213,139,
     87,  9,235,181, 54,104,138,212,149,203, 41,119,244,170, 72, 22,
    233,183, 85, 11,136,214, 52,106, 43,117,151,201, 74, 20,246,168,
    116, 42,200,150, 21, 75,169,247,182,232, 10, 84,215,137,107, 53};

//
// Compute a Dallas Semiconductor 8 bit CRC. These show up in the ROM
// and the registers.  (note: this might better be done without to
// table, it would probably be smaller and certainly fast enough
// compared to all those delayMicrosecond() calls.  But I got
// confused, so I use this table from the examples.)
//
uint8_t crc8_update(uint8_t crc, uint8_t data)
{
	return pgm_read_byte(dscrc_table + (crc ^ data));
}
#else
//
// Compute a Dallas Semiconductor 8 bit CRC directly.
// this is much slower, but much smaller, than the lookup table.
//
uint8_t crc8_update(uint8_t crc, uint8_t data)
{
  uint8_t inbyte = data;
  for (uint8_t i = 8; i; i--) {
    uint8_t mix = (crc ^ inbyte) & 0x01;
    crc >>= 1;
    if (mix) crc ^= 0x8C;
    inbyte >>= 1;
  }
	return crc;
}
#endif


#endif

#endif /* CRC_H_ */